Some people are just like that, and nothing you do will shake them. My brother and sister-in-law are like that with their kids/dog. Yes... yes... please tell me more about how it's perfectly acceptable your 2 year old dog still uses a pee pad and barks her head off every morning at 4am.
I loved hearing her songs when I was so busy doing my master's program!
But yeah, I try to just inform people when I do go to the store. I have some sort of "talk to me!" sign above my head (I think it comes from being a tour guide and interpreter in museums, etc.) so people will see me browsing the hamster aisles and just happily come and talk to me and ask my recommendations. Considering how hard it is to find an employee anyways in chain stores it helps. Sometimes if I see people struggling on water bottles, or something, I'll pop my head over and tell them "if you're looking for a hamster, I use XYZ".
I usually speak with people at least once or more every visit and generally I can drill a bit more sense into them than the employees.
My only real gripe is the lack of education on products for size, diabetes prone dwarfs, the fluffy bedding and then the use of mesh wheels in the display tanks.